A Commentary on the Book: “Expecting Better: Why the Conventional
Pregnancy Wisdom is Wrong and What You Really Need to Know” by Emily
Oster, Ph.D. Associate Professor of Economics, University of Chicago.
Multiple health authorities, including The United States Surgeon General, the American College of
Obstetricians and Gynecologists, the Canadian Society of Obstetricians and Gynecologists, and the
Public Health Agency of Canada, all advise that pregnant women and women who may become
pregnant should abstain from alcohol consumption. In her recent book, Dr. Oster challenges these
health authorities and this recommendation, arguing that moderate drinking during pregnancy is safe
(for example, a glass of wine per day). Although the definition of moderate drinking varies by country,
consumption of 1 standard drink/day (containing approximately 0.5 fl oz of pure ethanol in the U.S.) is
generally considered moderate drinking for non-pregnant women (Dufour, 1999). Dr. Oster’s book
suggests that the available scientific evidence does not support the recommendation to abstain from
alcohol use during pregnancy. This is not the case, as the current scientific evidence strongly
indicates that even light drinking during pregnancy can have long-lasting negative impact on brain
function in children that persists into adulthood. Below is a summary of key scientific studies that
have demonstrated significant adverse effects of alcohol at levels that can be achieved during light
drinking. We will begin with a review of studies that have been conducted with humans.
1. In a population cohort with low socio-economic status and mixed ethnicity (46% Caucasian
and 54% African-American) moderate alcohol exposure during the first trimester of pregnancy
was associated with significant deficits in verbal learning during adolescence (Willford et al.,
2004).
2. Other studies with different human populations have demonstrated a link between light
drinking and behavioral and cognitive problems during childhood and/or adolescence,
including alterations in working memory, attention and social interactions (Burden et al., 2005,
Coles et al., 1991, O'Leary et al., 2010, Sayal et al., 2007, Sood et al., 2001).
3. A recent study demonstrated that five variants of genes involved in alcohol metabolism in
children and their mothers were associated with cognitive ability at 8 years of age in children
born to mothers that reported drinking alcohol in moderation (1-6 drinks/week) during
pregnancy. This finding indicates that certain pregnant women may be more susceptible to the
effects of light drinking and that this may be related to genetic factors that regulate their ability
to metabolize alcohol (Lewis et al., 2012).
4. In a landmark longitudinal cohort study, Day and collaborators (Day et al., 2013) demonstrated
that low-moderate prenatal alcohol causes significant behavioral problems (for example,
attention deficits) that persist into adulthood (22 years of age).
5. A recent brain imaging study demonstrated that low-moderate ethanol exposure during fetal
development was associated with reductions in gray matter volume in several brain regions at
approximately 20 years of age (Eckstrand et al., 2012).
6. A recent analysis of several separate studies (i.e., a meta-analysis) found a significant
detrimental effect of light-moderate prenatal alcohol exposure on child behavior (Flak et al.,
2013). The problem behaviors identified in exposed children include increased need for
attention, deficient interactive play skills, and behavioral modulation alterations.
7. A study with humans found that newborns of mothers that consumed light amounts of alcohol
during pregnancy had a higher frequency of facial malformations and alterations in umbilical
cord artery contractility (Iveli et al., 2007).
Studies with laboratory animals support the findings of these human studies, demonstrating persistent
effects of light-moderate alcohol exposure on the brain (Valenzuela et al., 2012). The importance of
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animal studies is that other risk factors (for example, nutrition, genetics, environmental influences) are
controlled for and, therefore, the effects of alcohol exposure can be quantified.
1. Adult offspring of pregnant rats who consumed low levels of alcohol displayed deficits in
behavioral tests of learning and memory (Savage et al., 2002, Savage et al., 2010).
Alterations in the strength of transmission of information between neurons were identified as a
potential factor responsible for these deficits in learning and memory (Varaschin et al., 2010).
2. In addition, it was discovered that moderate alcohol exposure affects the generation of new
neurons in brain regions important for learning and memory, and this could also contribute to
the deficits observed in the exposed offspring (Choi et al., 2005, Uban et al., 2010, Akers et al.,
2011, Roitbak et al., 2011).
3. Exposure of pregnant macaque monkeys to moderate alcohol levels has also been shown to
impair motor coordination and delayed response speed in infant offspring (reviewed in
(Schneider et al., 2011)).
4. Long-lasting alterations in social behavior were recently demonstrated in adult offspring of rats
exposed to moderate alcohol levels during pregnancy (Hamilton et al., 2010).
5. Moderate alcohol exposure increased preference and consumption of alcohol-containing
solutions in adult offspring; adult rats from the ethanol group also exhibited increased cocaine
and amphetamine consumption after cocaine exposure (Barbier et al., 2009, Barbier et al.,
2008). This moderate prenatal alcohol exposure may increase the risk of developing
alcoholism and other addiction-related disorders.
6. A study with primates showed a reduction in aversive responses to repetitive tactile stimulation
in young adult monkeys exposed to low levels of alcohol throughout gestation that could result
in impaired control of sensory input (Schneider et al., 2008, Schneider et al., 2011).
In conclusion, the collective evidence from human and animal studies strongly suggests that even
light drinking during pregnancy can produce significant long-lasting alterations in the brain, adversely
affecting behavior, cognition, and social skills. Given the current state of the scientific evidence, the
safest course of action is to advise pregnant women and women who may become pregnant to avoid
drinking alcohol, even at low levels, during any stage of pregnancy.
James Reynolds, Ph.D. President
C. Fernando Valenzuela, M.D., Ph.D., Vice-president
Alexandre Medina, Ph.D., Treasurer
Jeffrey Wozniak, Ph.D. Secretary
Fetal Alcohol Spectrum Disorder Study Group-Research Society on Alcoholism
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